The present invention relates to an optical object identifying device that detects the type of an object in a noncontact manner and a printing apparatus that employs the device.
Generally, copiers and printers, which carry out recording processes while conveying recording media, have advanced in high-function, high-speed processing and high resolutions. The recording media to be used include a variety of types such as regular paper, glossy paper, OHP (Overhead Projector) sheets and so on. When printing is carried out on such a variety of types of recording media by a printer or the like (e.g., a printer of an ink-jet recording system), which is an image recording apparatus, it is required to form a high quality image by executing recording control in accordance with conditions of the recording medium, specifically, differences in the permeation rate and the time of drying of the ink depending on the type of the recording medium.
There are, for example, a first example of prior art and a second example of prior art as a device for detecting the types of the recording media of papers such as printing paper, resin films or sheets and so on.
In the first example of prior art, as shown in FIG. 10, a light-emitting device 41 and a photodetector 42 have been arranged at a prescribed angle with respect to a sheet 43 in order to reflect light emitted from the light-emitting device 41 on the sheet 3, and then to enter part of this reflected light into the photodetector 42. The quantity of light incident on the photodetector 42 has differed depending on the type (surface condition) of the sheet 43, and therefore, the type of the sheet 43 has been identified on the basis of this difference. Reference should be made to, for example, JP 10-198174 A.
In the second example of prior art, as shown in FIG. 11, one light-emitting device 41 and two photodetectors 42a and 42b have been arranged at prescribed angles with respect to the sheet 43, respectively. Specifically, a light-emitting device 41 and a first photodetector 42a have been arranged at same angle θ with respect to a direction perpendicular to the sheet 43, and a second photodetector 42b has been arranged at an angle θ/2 which is a half of the angle θ of the first photodetector 42a. The first photodetector 42a has received regular reflection light from the sheet 43, and the second the photodetector 42b has received diffuse reflection light from the sheet 43. Then, the type of the sheet 43 has been identified by a variance in the value of the quantity of light incident on the two photodetectors 42a and 42b depending on the sheet 43. Reference should be made to, for example, JP 2001-180843 A.
However, there are various types of sheets including regular paper, glossy paper, OHP paper, mat paper, a luster film, an inkjet postcard and so on. Thus, it has been difficult for the above-stated first and second examples of prior art to accurately identify all these types. Only the three types of regular paper, glossy paper and OHP paper have been able to be identified at the most.